EIGRP CHAPTER 9. Configuring Enhanced Interior Gateway Routing Protocol (EIGRP)

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1 CHAPTER 9 EIGRP This chapter provides information and commands concerning the following topics: Configuring Enhanced Interior Gateway Routing Protocol (EIGRP) EIGRP auto-summarization Load balancing: variance Bandwidth use Authentication Verifying EIGRP Troubleshooting EIGRP Configuration example: EIGRP Configuring Enhanced Interior Gateway Routing Protocol (EIGRP) Router(config)#router eigrp 100 Turns on the EIGRP process. 100 is the autonomous system number, which can be a number between 1 and 65,535. All routers in the same autonomous system must use the same autonomous system number. Router(config-router)#network Router(config-if)#bandwidth x Specifies which network to advertise in EIGRP. Sets the bandwidth of this interface to x kilobits to allow EIGRP to make a better metric calculation. TIP: The bandwidth command is used for metric calculations only. It does not change interface performance. Router(config-router)#no network Removes the network from the EIGRP process.

2 82 EIGRP Auto-Summarization Router(config)#no router eigrp 100 Disables routing process 100. Router(config-router)#network Router(config-router)#metric weights tos k1 k2 k3 k4 k5 Identifies which interfaces or networks to include in EIGRP. Interfaces must be configured with addresses that fall within the wildcard mask range of the network statement. A network mask can also be used here. Changes the default k values used in metric calculation. These are the default values: tos=0, k1=1, k2=0, k3=1, k4=0, k5=0 NOTE: tos is a reference to the original Interior Gateway Routing Protocol (IGRP) intention to have IGRP perform type-of-service routing. Because this was never adopted into practice, the tos field in this command is always set to zero (0). NOTE: With default settings in place, the metric of EIGRP is reduced to the slowest bandwidth plus the sum of all the delays of the exit interfaces from the local router to the destination network. TIP: For two routers to form a neighbor relationship in EIGRP, the k values must match. CAUTION: Unless you are very familiar with what is occurring in your network, it is recommended that you do not change the k values. EIGRP Auto-Summarization Router(config-router)#auto-summary Enables auto-summarization for the EIGRP process. NOTE: The default behavior of autosummarized changed from enabled to disabled was introduced in Cisco IOS Software Release 12.2(8)T. Router(config-router)#no autosummary Turns off the auto-summarization feature.

3 Load Balancing: variance 83 NOTE: The behavior of the autosummary command is disabled by default, beginning in Cisco IOS Software Release 12.2(8)T. This means that Cisco IOS Software will now send subprefix routing information across classful network boundaries. Router(config)#interface fastethernet 0/0 Router(config-if)#ip summaryaddress eigrp Enables manual summarization for EIGRP autonomous system 100 on this specific interface for the given address and mask. An administrative distance of 75 is assigned to this summary route. NOTE: The administrative-distance argument is optional in this command. Without it, an administrative distance of 5 is automatically applied to the summary route. CAUTION: EIGRP automatically summarizes networks at the classful boundary. A poorly designed network with discontiguous subnets could have problems with connectivity if the summarization feature is left on. For instance, you could have two routers advertise the same network /16 when in fact they wanted to advertise two different networks /24 and /24. Recommended practice is that you turn off automatic summarization if necessary, use the ip summary-address command, and summarize manually what you need to. Load Balancing: variance Router(config)#router eigrp 100 Creates routing process 100 Router(config-router)#network Router(config-router)#variance n Specifies which network to advertise in EIGRP Instructs the router to include routes with a metric less than or equal to n times the minimum metric route for that destination, where n is the number specified by the variance command

4 84 Authentication NOTE: NOTE: If a path is not a feasible successor, it is not used in load balancing. EIGRP supports up to six unequal-cost paths. Bandwidth Use Router(config)#interface serial 0/0 Router(config-if)#bandwidth 256 Router(config-if)#ip bandwidth-percent eigrp Sets the bandwidth of this interface to 256 kilobits to allow EIGRP to make a better metric calculation. Configures the percentage of bandwidth that may be used by EIGRP on an interface. 50 is the EIGRP autonomous system number. 100 is the percentage value. 100% * 256 = 256 kbps. NOTE: By default, EIGRP is set to use only up to 50 percent of the bandwidth of an interface to exchange routing information. Values greater than 100 percent can be configured. This configuration option might prove useful if the bandwidth is set artificially low for other reasons, such as manipulation of the routing metric or to accommodate an oversubscribed multipoint Frame Relay configuration. NOTE: The ip bandwidth-percent command relies on the value set by the bandwidth command. Authentication Router(config)#interface serial 0/0 Router(config-if)#ip authentication mode eigrp 100 md5 Router(config-if)#ip authentication key-chain eigrp 100 romeo Router(config-if)#exit Enables Message Digest 5 algorithm (MD5) authentication in EIGRP packets over the interface. Enables authentication of EIGRP packets. romeo is the name of the key chain. Returns to global configuration mode.

5 Authentication 85 Router(config)#key chain romeo Router(config-keychain)#key 1 Identifies a key chain. The name must match the name configured in interface configuration mode above. Identifies the key number. NOTE: The range of keys is from 0 to The key identification numbers do not need to be consecutive. At least 1 key must be defined on a key chain. Router(config-keychain-key)#keystring shakespeare Identifies the key string. NOTE: The string can contain from 1 to 80 uppercase and lowercase alphanumeric characters, except that the first character cannot be a number. Router(config-keychainkey)#accept-lifetime start-time {infinite end-time duration seconds} Optionally specifies the period during which the key can be received. NOTE: The default start time and the earliest acceptable date is January 1, The default end time is an infinite period. Router(config-keychain-key)#sendlifetime start-time {infinite endtime duration seconds} Optionally specifies the period during which the key can be sent. NOTE: The default start time and the earliest acceptable date is January 1, The default end time is an infinite period. NOTE: For the start time and the end time to have relevance, ensure that the router knows the correct time. Recommended practice dictates that you run Network Time Protocol (NTP) or some other time-synchronization method if you intend to set lifetimes on keys.

6 86 Troubleshooting EIGRP Verifying EIGRP Router#show ip eigrp neighbors Router#show ip eigrp neighbors detail Displays the neighbor table. Displays a detailed neighbor table. TIP: The show ip eigrp neighbors detail command verifies whether a neighbor is configured as a stub router. Router#show ip eigrp interfaces Router#show ip eigrp interfaces serial 0/0 Router#show ip eigrp interfaces 100 Router#show ip eigrp topology Shows information for each interface. Shows information for a specific interface. Shows information for interfaces running process 100. Displays the topology table. TIP: The show ip eigrp topology command shows you where your feasible successors are. Router#show ip eigrp traffic Router#show ip route eigrp Shows the number and type of packets sent and received. Shows a routing table with only EIGRP entries. Troubleshooting EIGRP Router#debug eigrp fsm Router#debug eigrp packet Router#debug eigrp neighbor Router#debug ip eigrp neighbor Router#debug ip eigrp notifications Displays events/actions related to EIGRP feasible successor metrics (FSM) Displays events/actions related to EIGRP packets Displays events/actions related to your EIGRP neighbors Displays events/actions related to your EIGRP neighbors Displays EIGRP event notifications

7 Configuration Example: EIGRP 87 Configuration Example: EIGRP Figure 9-1 illustrates the network topology for the configuration that follows, which shows how to configure EIGRP using the commands covered in this chapter. Figure 9-8 Network Topology for EIGRP Configuration s0/ /24 Austin fa0/ /24 s0/ /24 DCE Houston fa0/ /24 s0/0 Corporate Network EIGRP Routing with MD5 Authentication Between Routers / /24 Austin Router Austin>enable Austin#configure terminal Austin(config)#interface serial 0/0 Austin(config-if)#ip address Austin(config-if)#ip authentication mode eigrp 100 md5 Austin(config-if)#ip authentication key-chain eigrp 100 susannah Austin(config-if)#no shutdown Austin(config-if)#interface fastethernet 0/1 Austin(config-if)#ip address Austin(config-if)#no shutdown Austin(config-if)#router eigrp 100 Moves to privileged mode. Moves to global configuration mode. Assigns the IP address and netmask. Enables MD5 authentication in EIGRP packets. Enables authentication of EIGRP packets. susannah is the name of the key chain. Enables the interface. Assigns the IP address and netmask. Enables the interface. Enables EIGRP routing.

8 88 Configuration Example: EIGRP Austin(config-router)#no auto-summary Austin(config-router)#network Austin(config-router)#key chain susannah Austin(config-keychain)#key 1 Austin(config-router)#eigrp logneighbor-changes Austin(config-keychain-key)#keystring tower Austin(config-keychain-key)#acceptlifetime 06:30:00 Apr infinite Austin(config-keychain-key)#sendlifetime 06:30:00 Apr :45:00 Apr Austin(config-keychain-key)#exit Austin(config)#exit Austin#copy running-config startupconfig Disables auto-summarization. Changes with neighbors will be displayed. Advertises directly connected networks (classful address only). Identifies a key chain name, which must match the name configured in interface configuration mode. Identifies the key number. Identifies the key string. Specifies the period during which the key can be received. Specifies the period during which the key can be sent. Returns to global configuration mode. Returns to privileged mode Saves the configuration to NVRAM. Houston Router Houston>enable Houston#configure terminal Houston(config)#interface serial 0/1 Houston(config-if)#ip address Houston(config-if)#ip authentication mode eigrp 100 md5 Houston(config-if)#ip authentication key-chain eigrp 100 eddie Moves to privileged mode. Moves to global configuration mode. Assigns the IP address and netmask. Enables MD5 authentication in EIGRP packets. Enables authentication of EIGRP packets. eddie is the name of the key chain.

9 Configuration Example: EIGRP 89 Houston(config-if)#clock rate Houston(config-if)#no shutdown Houston(config-if)#interface fastethernet 0/1 Houston(config-if)#ip address Houston(config-if)#no shutdown Houston(config-if)#router eigrp 100 Houston(config-router)#no auto-summary Houston(config-router)#network Houston(config-router)#key chain eddie Houston(config-keychain)#key 1 Houston(config-router)#eigrp logneighbor-changes Houston(config-keychain-key)#keystring tower Houston(config-keychain-key)#acceptlifetime 06:30:00 Apr infinite Houston(config-keychain-key)#sendlifetime 06:30:00 Apr :45:00 Apr Houston(config-keychain-key)#exit Houston(config)#exit Houston#copy running-config startupconfig Sets the clock rate. Enables the interface. Assigns the IP address and netmask. Enables the interface. Enables EIGRP routing. Disables auto-summarization. Changes with neighbors will be displayed. Advertises directly connected networks (classful address only). Identifies a key chain name, which must match the name configured in interface configuration mode. Identifies the key number. Identifies the key string. Specifies the period during which the key can be received. Specifies the period during which the key can be sent. Returns to global configuration mode. Returns to privileged mode. Saves the configuration to NVRAM.